Steering Rack Complementary Geometry for Twist Prevention
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Solution Overview
Problem
Steer-by-wire steering systems with ball screw drives lack inherent torsion prevention, necessitating additional components to prevent torsion in the toothed rack, unlike rack-and-pinion arrangements which provide automatic torsion prevention.
Innovation Solution
A steering system with a toothed rack having a convex or concave cross-section that fits within a housing with complementary concave or convex formations, creating a positive-locking connection for torsion prevention, and an intermediate element for low-friction sliding friction, potentially with a wave form or metal projections for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a ball screw drive is used in a steer-by-wire steering system, then the steering torque can be applied, but there is no inherent torsion prevention of the toothed rack
Solution Approach 1:
The toothed rack is given an asymmetric cross-sectional shape (convex or concave) that complements the corresponding asymmetric shape in the housing. This asymmetric geometry creates a positive-locking connection that prevents torsion of the toothed rack while allowing axial movement for steering operation.
2Reliability
If a pressure piece is arranged opposite the pinion in a rack-and-pinion arrangement, then torsion prevention is automatically provided, but the device complexity increases
Solution Approach 1:
The torsion prevention function is merged into the housing structure itself through the complementary convex/concave formations. Instead of adding a separate pressure piece or torsion prevention member, the housing's internal geometry directly provides the positive-locking connection that prevents toothed rack torsion.
Solution Approach 2:
The housing serves multiple functions: it contains the ball screw drive, provides structural support, and through its complementary convex/concave formations, provides torsion prevention of the toothed rack. This multi-functionality eliminates the need for dedicated torsion prevention components.
3Object-affected harmful factors
If an intermediate element is arranged between the housing and toothed rack, then low-friction and low-wear sliding friction is ensured, but the device complexity increases
Solution Approach 1:
An intermediate element is introduced between the toothed rack and housing to serve as a mediator that reduces friction and wear. This intermediate element features a wave form or sinusoidal configuration that enables low-friction sliding motion while maintaining the positive-locking torsion prevention function.
Data Source
AI summary
A steering system for steering a wheel of a vehicle includes a track rod for deflecting the wheel, a rack which, by axial movement, leads to control of the track rod, and a housing. The rack is at least partially arranged within the housing. The rack has a convex and/or concave cross-sectional portion. The housing-mounted complementary geometry includes a complementary concave and/or convex shaping, as a result of which a form-fitting connection is produced for realizing the twist prevention.